1. Field of the Invention
The present invention relates to an image reading apparatus for reading an image of a document.
2. Description of Related Art
There is an image reading apparatus for reading an image of a document conveyed by a document feeder. A document bundle, which is bound by a stapler for example, may be erroneously set to the image reading apparatus.
Japanese Patent Laid-open Publication No. 2009-51585 discusses an image reading apparatus having a configuration to suspend conveyance of sheets in a case where documents set to the image reading apparatus is bound by a stapler. In Japanese Patent Laid-open Publication No. 2009-51585, two sensors are provided at a downstream side of a separation roller for feeding documents by separating the documents one by one in a direction intersecting with a conveyance direction of the document. The image reading apparatus detects a skew amount of the document based on a difference between passing timings of the leading edge of the document detected by the two sensors, determines that the documents are stapled if the skew amount is larger than a predetermined threshold, and suspends a conveyance operation for conveying the document. In the configuration to suspend conveyance of the document in a case where the skew amount of the document is larger as it is discussed in Japanese Patent Laid-open Publication No. 2009-51585, the following issue may occur if the documents having different sizes in a width direction orthogonal to the conveyance direction of the document are mixedly placed on a paper feed tray of the document feeder.
In a case where documents having different sizes in the width direction are mixed (hereinafter referred to as mixture of different widths), large skews of the documents may occur when the documents are fed from the paper feed tray. This is because, positions of side regulating plates which are accommodated in the paper feed tray for regulating both sides of the documents in the width direction is fixed according to a document having the largest size in the width direction among the documents of the document bundle set in the paper feed tray. Among the documents of the document bundle of a mixture of different widths, the document having the largest size in the width direction is fed such that both sides of the document is regulated by the side regulating plates when it is fed, whereas the document having a relatively smaller size in the width direction tends to be skewed since the document is not regulated by the side regulating plates from both sides.
Accordingly, in a case where the documents having different widths are fed, an erroneous determination that the documents are bound might be made since a large skew occurs in the document having narrower width although the document is actually not stapled by a stapler.